The present invention relates to a physiological food salt product which primarily consists of minerals and in whose formulation an alkaline earth metal component or components are brought to an appropriate form with acceptable taste and hygroscopic properties. The invention also relates to the use of a salt product prepared according to the method.
In the preparation, preservation or seasoning of foods in a variety of cases, with respect to the use of food salt products, it is presently an important aim to avoid excessive inclusion of common salt, i.e. sodium chloride, NaCl, in the formulation of the food product. The reason for this attempt is the clearly documented harmful effect of NaCl on human health. When the daily consumption of NaCl by a person in the Western countries is estimated to be 170 meq (9.9 g), morbidity on arterial hypertension and mortality on myocardial infarction are common even with daily intake of 100 meq (5.8 g). When the daily dose is less than 50 meq (2.9 g), morbidity is indicated to be low. Consequently, the above-mentioned value 50 meq per day can be considered the recommended maximum daily intake of NaCl.
It has been found in different cases that a daily intake of magnesium, Mg, reduces blood pressure. The recommended dietary allowance (RDA) indicated for magnesium is 4.5 mg/kg/day, resulting in calculated values of 350 to 400 mg per day for adult male population and 280 to 300 mg per day for women, correspondingly. For the above-mentioned reasons, there is a strong need to develop a substitute or modification for common salt, which will fulfill not only the physiological recommended values but also other requirements, such as taste and good sprinklability in its most common form of usage.
The RDA value for calcium, Ca, is indicated to be 800 to 1200 mg per day for adult population. Although the supply of calcium is often sufficient, particularly when the diet is based on milk products, it can be considered appropriate to include calcium in table salt, for example due to an increased need of Ca during pregnancy or during adolescence.
To combine physiologically sufficient alkaline earth contents with food salt formulations has been problematic in practice, primarily because other salts than chlorides (sulphates, phosphates, carbonates, etc.) can hardly be used because of their physiological unsuitability, bitter taste and/or poor solubility.
When alkaline earth metal chlorides are added to food salt in connection with the preparation process, one must, however, solve in a satisfactory manner their strong hygroscopicity, which means the tendency of deliquescence of the product under the effect of humidity in the air. Furthermore, the taste of these chlorides is pungently salty and thus too different from the taste of NaCl.
The same properties apply to carnallite, MgCl2xc3x97KClxc3x976H2O, present in natural salt deposits which normally contains such quantities of coprecipitated bromides that its nutritional use as such is out of question.
Upon studying the prior art related to the invention, it is found that the development of table salt products has recently been focused on products containing potassium, K, or potassium and magnesium, K and Mg, whereby the main purpose is to reduce the intake of sodium, Na, in food, the main criteria for commercial utilization being acceptable taste. Consequently, methods have been introduced to prepare such mixtures of NaCl, KCl and MgCl2 in which MgCl2 or its potassium double salt imitating the natural carnallite is protected from air humidity by means of alkali metal chlorides. Two patent applications that are close to these subjects should be mentioned, WO A1 92/16117 (A23L 1/237) and WO A1 92/18668 (A23L 1/237). Of these, the former presents a method for coating the hygroscopic component of the salt with a non-hygroscopic material. The latter patent application presents a method for treatment of NaCl-K/Mg salts, which method comprises quick drying of the solution prepared of the salts and is intended for producing a stable multi-component salt mixture.
Patent application WO 90/00522 (A23L 1/237) describes a synthetic method for preparing a salt which imitates carnallite for a food salt product by evaporating a solution which contains potassium chloride and magnesium chloride in equivalent ratios and by heat treatment of the obtained evaporation residue to stabilize the product. However, it is industrially impractical to remove scale deposits from the evaporating apparatus, and the method cannot thus be realized as a continuous process. Moreover, it has been found in check-up studies relating to the method that a dried evaporation residue obtained with e.g. a rotatory evaporator is as hygroscopic as natural carnallite, and that as a result of the heat treatment, hydrochloric acid is emitted from the product, which results in that the solubility of the product to water, the pH of the solution, and thereby its taste are changed to the adverse direction.
Aalso patent application WO 88/09131 (A23L 1/237) should be mentioned as related to the invention. The application presents a salt substitute which contains 50% of free ammonium chloride NH4Cl admixed mechanically to phosphates and sugar which adjust the acidity of the 20 product. Continuous use of the product according to the formulation may, however, be physiologically doubtful, because the calculatory ammonium content will thus rise to a level of 16.8%.
Furthermore, as prior art connected with the invention, two Finnish patent applications should be mentioned, No. 961229 and No. 970323, as well as international application WO 98/32343 (A23L 1/237) related to the latter, in which, to eliminate the hygroscopicity, an amino acid complex is formed from alkaline earth chlorides, particularly with glycine, which is also the simplest amino acid. However, a closer study of the technique presented in the patents has revealed that the aims of the patents cannot be achieved to the described extent, for the following reasons.
For example, MgCl2xc3x976H2O forms three different complexes with glycine, which have been found to be in a balance with each other according to the following equation: 
For example, a compound prepared with equivalent ratios of MgCl2 and glycine is thus normally a mixture which does not fulfill the criterion of hygroscopicity at high air humidity values. Moreover, it is not possible to isolate amino acid complexes from a concentrated solution by centrifugation, but the solution must be fully evaporated, which complicates industrial production. Furthermore, it seems that adverse changes take place in the taste and colour of the final product even in a short time interval, possibly due to oxidation of the organic component.
In any case, none of the products according to any of the above-mentioned applications fulfills all the requirements set above for the invention. The same applies to commercially available Na-K-Mg table salts, examples of which include the almost identical products Seltine(copyright) and Pan Salt(copyright) whose composition comprises the compounds NaCl, KCl and MgSO4xc3x977H2O (12%) in a mechanical mixture. When the intake of magnesium is calculated from e.g. the above-mentioned commercial products with an average daily use of 7.5 g, the daily dose obtained for magnesium is 88 mg, which is fully insufficient in view of the above-mentioned recommended values. In these products, the hygroscopic properties are under control, but it has not been possible to eliminate the disadvantages of the sulphate, of which an increased excretion of calcium possibly caused by the sulphate ion should be mentioned. Furthermore, analyses of the compositions of both products have revealed MgSO4 contents differing from the given values, which may be primarily due to the fact that this salt has a different crystalline form and density than the alkali metal chlorides, which results in the separation of magnesium sulphate from the mixture.
It is disclosed in prior art that ammonium carnallite type compounds of alkaline earth metals, particularly the corresponding magnesium salt, have been used for preparing anhydrous alkaline earth chlorides by a pyrolytic method for technical purposes, of which the most important is the electrolytic preparation of magnesium metal from MgCl2 melt in a process which is now outdated (British patent 351 845 from the year 1931 and German Offenlegungsschrift 1 567 937 from the year 1970). The uses in question do not, however, fall into the category of the present application, and the patent publications in question do not discuss the hygroscopic properties of the prepared products.
The purpose of the invention is to introduce a method, by which it is possible to eliminate the above-mentioned drawbacks related to the preparation of food salts and to make a product containing the desired ions, particularly alkaline earth metal chlorides, which fulfills the requirement of sufficiently low hygroscopicity as well as makes it possible to achieve the objectives related to the taste and nutritional properties set for the salt product.
To achieve the above-mentioned aims, the invention is primarily characterized in what will be presented in the characterizing part of the appended claim 1. By means of ammonium chloride salts of the alkaline earth metals Mg and Ca, it is possible to produce a nutritional salt product which contains the desired ions but whose physical properties are also suitable for practical applications.
The method of the invention for preparing physiological food salts is based on the surprising finding that when ammonium chloride is added into substantially concentrated solutions, normally aqueous solutions, which contain alkaline earth metal chloride or chlorides, and can preferably also contain potassium chloride and possible other components and/or micronutrients affecting primarily the taste, it is possible to obtain, particularly in the presence of magnesium chloride, carnallite-type crystalline precipitations which fulfill the above-mentioned requirements relating to low hygroscopicity and the taste. Furthermore, the taste, primarily the acidity, of the obtained carnallite-type salts can be influenced preferably by changing the pH value of the mother liquor with bases, preferably ammonia, and/or by treating the product separated from the mother liquor at suitably selected temperatures.
With reference to the invention, it has been surprisingly found that ammonium carnallite, whose formula can be given either as MgCl2xc3x97NH4Clxc3x976H2O or MgNH4Cl3xc3x976H2O, has the particular property to co-precipitate hygroscopic chlorides, such as calcium, chloride CaCl2 or potassium carnallite MgKCl3xc3x976H2O from the mother liquor to mixed crystal forms which have no hygroscopicity or in which the property is substantially suppressed.
The use and modification of ammonium chloride hydrates of alkaline earth metals in the above-described manner to prepare the present physiological food salt product and to control its properties is not disclosed in the prior art. It is thus a new inventive idea.
The inclusion of hygroscopic alkaline earth metal chlorides or their double salts, such as potassium carnallite, in sprinklable food salt products has been previously difficult or almost impossible. These impediments can be eliminated by forming a crystalline ammonium chloride adduct from the salts.